Modified cracking process



Patented Nov. 22, 1966 3,287,438 MODIFIED CRACKING PROCESS I Kenneth J. Frech, Tallmadge, Ohio, assignor to The Goodyear Tire 8: Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Filed Apr. 19, 1966, Ser. No. 543,540 9 Claims. (Cl. 260-680) This application is a continuation-in-part of application Serial No. 222,178 filed September 7, 1962, now abandoned.

This invention relates to a promoted cracking process for certain olefins. More specifically it relates to a method of improving the cracking of certain olefins. Most specifically it relates to methods of improving the efficiency of cracking of certain olefins to form specific diolefins and paraffinic hydrocarbons or to form certain other specific olefins.

It is known that certain olefins may be thermally decomposed or cracked by subjecting them to elevated temperatures; for instance, olefins which have in their molecular make-up a carbon-carbon bond which is in a position beta to the double bond will, under proper conditions of heat, time and pressure undergo a scission of the carbon-carbon bond in the position beta to the double bond. By the terms cracking, decomposing, cracked, or decomposed as employed throughout this specification and claims is meant that the olefin molecule splits into two or more fragments at the carbon-carbon bond which is in a position beta to the double bond. This will be explained in more detail later.

The thermal decomposition or cracking of olefins is usually conducted in a closed zone or reactor and is usually conducted in the absence of oxygen. The temperatures employed usually vary from about 300 to about 1,000 C. Usually this thermal cracking process is conducted While the olefins are in a gaseous state. The olefins may be cracked in relatively pure form or a diluent may be employed.

Employing the most favorable conditions conducive to the cracking of olefins, these conditions being temperature, residence time in the cracking zone, the ratio of the olefin to the diluent if any be employed, it has 'been found that olefins decompose in fairly low yields. As employed in this application the term yield is meant to connote the decomposition of the olefin feed stock per pass through the cracking zone.

It is, therefore, the object of this invention to provide a method whereby the per pass yield of the desired products produced by cracking these olefins is increased. Another object is to provide a method whereby the residence time in the heating zone and the temperature of the heating zone may be decreased to prevent undesirable side reactions from taking place. Still other objects are to provide cracking promoters which will allow greater yields to be obtained in the cracking of these olefins. Still other objects will be apparent as the description proceeds.

To further explain what is meant by a carbon-to-carthe double bond and the location of the side group on the chain, if any be present. It is believed that this best can be illustrated by the following discussion. When an olefin containing 6 carbon atoms with a side group, i.e., a methyl group attached to the second carbon atom of the main or straight portion of the chain, and the double bond in the 2 position, such an olefin being 2-methyl pentene-2, is subjected to cracking conditions, the predominant products obtained are Z-methyl butadiene-l,3 (isoprene) which is a diolefin, and methane, a parafiin. On the other hand, if a 6 carbon olefin such as Z-methyl pentene-l, which has the double bond in the 1 position and the methyl group in the 2 position, is cracked it will yield as the predominant products two other olefins, isobutylene and ethylene. When still another isomeric hexene such as 4-methyl pentene-l is cracked, two moles of the olefin propylene are formed. These differences in products obtained, when different isomeric forms of olefins containing the same number of carbon atoms are cracked, are due to the fact that olefins crack at the position beta to the double bond, that is to say the carboncarbon bond which is two carbon atoms removed from the double bond, is the carbon-to-carbon bond at which the scission occurs. There are certain olefins which do not contain in their molecular make-up a carbon-carbon bond in the position beta to the double bond and, therefore, do not undergo the same reactions when subjected to thermal decomposition conditions. These olefins are ethylene, propylene, butene-2, isobutene, 2-methyl butene-2, and 2,3-dimethyl butene-2, and are usually referred to as refractory olefins. Since these olefins do not undergo similar chain scission as do olefins which contain in their molecule a carbon-to-carbon bond in the beta position to the double bond, these refractory olefins are not considered to be within the scope of the olefins which are to be cracked in accordance with this invention.

It has been found that the objects of this invention are accomplished by subjecting olefins which have in their molecule a carbon-carbon bond which is in a position beta to the double bond to conditions of temperature and time suitable or sufiicient to cleave the carbon-to-carbon bond which is in a position beta to the double bond while said olefin is in the presence of a promoter comprising a mixture of a material which will supply an SH radical and at least one hydrocarbon selected from the group consisting of benzene, toluene and xylene.

The practice of this invention may be carried out in any conventional manner which is usually employed in the thermal cracking of olefins.

Generally, the conditions which may be employed in the practice of this invention may vary widely; for instance, the cracking temperature may vary broadly from about 400 C. to about 900 C. However, more preferred cracking temperatures are from about 600C. to about 750 C. The time in which the olefins are in the cracking zone may range broadly from about 0.001 to about 3.0 seconds. However, it is more preferable to employ times varying from about 0.05 to about 0.5 second. These times which are referred to are usually called residence times and are defined as the time required for one mol of gas, whether it be pure olefin or in mixture with the diluents, to pass through the cracking zone.

As was stated above, generally olefins are cracked either as pure hydrocarbons or as mixtures with other diluent gases. These diluent gases may be such materials as steam, carbon dioxide, hydrogen, parafiins, the refractory olefi'ns, or any other inert gaseous substance which does not materially aflect the cracking process or react with either the feed stock or products other than to act generai'ly as a diluent. The nation of this diluent gas may be widely varied depending on conditions, but it is usually employed in mol ratios of from about 0.5/1 to about 15/1 moles of diluent per mole of ole-fin. If more than 15/ 1 mol ratio is employed, the process tends to become uneconomical. Therefore, itis preferred to use a diluent to olefin mol ratio'ranging from about Q/ 1 to about 4/ 1.

The pressure employed in the cracking zone may be varied from a low of 10 milliliters of mercury to 500 pounds per square inch gauge or even higher. However, it is usually preferred that the pressure range from about atmospheric to about 100 p.s.i. with about 1-2 atmospheres being preferred.

, As was stated before, the activator or'promoter employed in this invention to enhance the cracking of olefins which have in their molecules a carbon-to-carbon bond in a position beta to the double bond is a mixture of a material which will supply an SH radical and at least one hydrocarbon selected from the group consisting of benzene, toluene, and xylene or mixtures thereof.

The SH radical which is employed to increase the efficiency obtained when olefins iare cracked inaccordance with the practice of this invention may be provided by various means. Hydrogen sulfide will under the conditions employed in the practice of this invention dissociate to form hydrogen and an SH radical. Low molecular weight mercaptans such as ethyl, normal propyl, isopropyl, normal butyl, isobutyl and the amyl and hexyl mercaptans will also form an SH radical at the temperatures employed in the cracking operation. It is believed that any aliphatic mercaptan will decompose at the operating conditions to give hydrogen sulfide and an olefin with the same number of carbon atoms as originally contained in the aliphatic mercaptan. This hydrogen sulfide then provides the SH radical as indicated above. Thus, in the practice of this invention not only can hydrogen sulfide gas be employed but any other material may be employed which under the operating conditions decomposes to provide hydrogen sulfide. Of these methods which may be employed to supply SH radicals in the practice of this invention hydrogen sulfide is the preferred material.

1 The SH radical employed in the practice of this invention may be used in amounts varying from about 0.5 to about 50 mol percent of SH radical :based on the total mols of the olefin to be cracked. It has been found, however, that. excellent results have been obtained by employing from about 5 to about mol percent of the SH radical. It should be noted that one mol of the SH radical is produced for each mol of the SH radical-producing compound employed. Since one mol of hydrogen sulfide provides one mol of SH radical these amounts are applicable to the amount of hydrogen sulfide employed as well.

The hydrocarbon component of the promoter of this invention may be benzene, toluene or xylene and various substituted forms of benzene, toluene and xylene and mixtures thereof. Representative of such substituted materials are chlorobenzene, chlorotoluene, and the like and various other inert substituents which may be substituted in these three hydrocarbons.

The promotermay be added to the cracking mixture in various ways. A most convenient method is to dissolve the materials .acting as the promoter in the olefin feed stock. They may also be added as separate components to the cracking furnace.

The amount of promoter employed in the practice of this invention has not been found to be too critical. Of course, sufiicient promoter should be employedto obtain some benefit and for the sake of economy no. more promoter should be employed than is necessary. Gencrally, it has been the practice to employ at least 1.0 mole percent of each component of the mixture, with about 5 to about 10 mol percent of each component being preferred. However, under certain conditions it is possible that less than 2 mole percent may show beneficial effects. The amount of promoter employed is calculated on the basis of the mols of SH radical and the hydrocarbon employing SH radical as one mol. (Thus, one mol of mercaptan or one mol of H 8 supplies one mol of SH radical.) The ratio of the hydrocarbon component of the promoter to the SH radical component may be varied widely but usually a ratio from about 1/1 to about 20/ 1 should be employed. In general it can be said that no further improvement is obtained where more than 50 mol percent of the promoter is employed. (All of these mol percentage calculationsare based on the total mol of olefin to be cracked.)

The practice of this invention is illustrated by the following experiments which are to be interpreted as representative rather than restrictive of the scope of this invention. The results and conditions of the cracking experiments are reported in table form.

. All of the cracking experiments were performed in a reactor assembly consisting of a-hairpin coil prepared from /4-inch OD 316 stainless steel tubing. This coil reaction was immersed in a bed of fluidized heat transfer powder which was microspheroidal silica-alumina cracking catalyst. The heat transfer powder was heated both by electrical resistance heaters and by combusting a natural gas flame in the fluidized powder bed. The temperature gradient from top to bottom of the bed was never more than 5 to 6 C. and the gradient from the fluidized bed to the tube walls was about 5-6 C. The temperatures within the fluidized bed were measured by conventional thermocouple techniques as were the temperatures within the cracking zone. The procedure employed was to bring the heat transfer powder up to about 500 C. employing the electrical resistance heaters while fluidizing the heat transfer powder with air. Then the natural gas burner was employed to bring the heat transfer powder up to the desired cracking or operating temperature. The toluene was added to the olefin feed stream. The n-propyl mercaptan was added separately to the cracking reactor along with the cracking mixture. The water, olefin and promoter were pumped at the proper rates necessary to produce the H O/hydrocarbon ratio desired and to give the desired residence time of the materials in the cracking zone or cracking reactor. When all variables had been adjusted to give the desired operating conditions the products resulting from the cracking operation were collected by means of cooled receivers, if liquid, and were metered at atmospheric and room temperature conditions, ifgas. The products'were analyzed for content and yields by conventional analytical methods.

The results of each ofthe experiments in the following examples as well as the operating conditions are reported in tables below. Column 1 is the experiment number; column 2 is the residence time in seconds; column 3 is the temperature employed in the cracking operation in degrees centigradc; column 4 is the material employed as the particular cracking promoter with the amount employed in mol precent based on the olefin to be cracked (where no promoter was employed this column lists none); column 5 is the mol percent yield of isoprene per pass based on the 3-methyl pentene-2 charged.

EXAMPLE in this example S-methyl pentene-Z was the olefin cracked, except in Experiment No. 4'where Z-methyl pentene-Z was used. Steam was used as the diluent at a mol ratio of water to hydrocarbon of approximately 3/1. Experiment No. 1 illustrates the effect of the addition of toluene alone. Experiment No. 2 employed no Experi- Time Temper- Promoter Yield ment No. ature 0. 675 Toluene l7. 9 0.15 675 None 17. 3 0. 146 675 n-Propylmercaptan 0 28. 7

Toluene 5. O 0. 296 651 n-Propyl mercaptan.-. 5. 0 18. 8

From the above experiments it can be seen that the practice of this invention as exemplified by 5 mol percent normal mercapta-n in mixture with 5 mol percent toluene (Experiment No. 3) does show a distinct improvement of a true thermal cracking process as exemplified by Experiment N0. 2 and over the effect of toluene alone as exemplified by Experiment No. 1. Furthermore, Experiment No. 3 is a distinct improvement over Experiment No. 4 in which 2-methyl pentene-Z was cracked in the presence of 5 mol percent normal mercaptan alone at a slightly lower temperature and longer time. Other similar results and improvements may be obtained when the general techniques of these experiments and the other specific teachings mentioned elsewhere in this application are applied to other olefins having in their molecules a carbon-t0- carbon bond in a position beta to the double bond, especially when the olefin is Z-methyl pentene-Z.

Representative among the olefins which will decompose to form predominantly butadiene-1,3 when cracked in accordance with the practice of this invention are pentene-2; heXene-2; 3-methyl pentene-l; cyclohexene, 3- methyl butene-l; Z-heptene; 3-methyl heXene-l; S-methyl hexene-2; 2-octene; S-methyl heptene-Z; 3,5-dimethyl hexene-l; 3,4,4-trimethyl pentene-l; 6-methyl heptene-Z; nonene-2; and 3-methyl octene-l.

Representative among the olefins which will decompose to form predominantly Z-methyl butadiene-1,3 or isoprene when cracked in accordance with the practice of this invention are 2-methyl pentene-Z; 3-methyl pentene-Z; 2- ethyl butene-l; 3,3-dimethyl butene-l; 2,3-dirnethyl butene-l; Z-methyl hexene-2; 3-methyl hexene-Z; 2-ethyl pentene-l; 2,3-dimethyl pentene-l; 3,3-dimethyl pentene-l; 2- methyl heptene-Z; 3-methyl heptene-2; 2-ethyl hexene-l; 3,3-dimethyl hexene-l; 2,5-dimethyl hexene-2; 3,5-dirnethyl hexene-Z; 4-methyl-2-ethyl pentene-l; 2,3,4-trimethyl pentene-l; 3,3,4-trimethyl pentene-2; Z-methyl octene-2; 3-methyl octene-Z; 3,3-dimethyl heptene-l; 2,5-dimethyl heptene-Z; 2,6-dimethyl heptene-2; 5-methyl-2-ethyl hexene-l; 3,3,5-trimethyl hexene-l; and 2,5,5-trimethyl hexene-Z.

Representative among the olefins which will decompose to form predominantly Z-ethyl butadiene-1,3 when cracked in accordance with the practice of this invention are 3- ethyl pentene-Z; 2-ethyl pentene-2; 3-ethyl hexene-2; 3- methyl-Z-ethyl pentene-l.

Representative among the olefins which will decompose to form predominantly 2,3-dimethyl butadiene-1,3 when cracked in accordance with the practice of this invention are 2,3-dimethyl pentene-2; 3-methyl-2-ethyl butene-l; 2,3,3-trimethyl butene-l; 2-isopropyl pentene-l; 2,3,3-trimethyl pentene-l; and 2,3-dimethyl heptene-Z.

Representative among the olefins which will decompose to form predominantly 3-methyl pentadiene-1,3 when cracked in accordance with the practice of this invention are 3-Inethyl hexene-3; 3-methyl heptene-3; 3,4-dimethyl hexene-Z; 3,6-dimethyl heptene-3.

Representative among the olefins which will decompose to form predominantly Z-methyl pentadiene-l,3 and 4- 6 methyl pentadiene-1,3 when cracked according to the practice of this invention are 2,4-dimethyl pentene-Z; Z-methyl heptene-3; 4,4-dimethyl hexene-2; 2-.propyl pentene-Z; 2- methyl-3-ethyl pentene-l; 2,6-dimethyl heptene-3 and 2- propyl hexene-l.

Representative among the olefins which will decompose to form predominantly piperylenes when cracked in accordance with the practice of this invention are hexene-3; 4-methyl pentene-Z; heptene-3; 4-methyl hexene-2; octene- 3; 4-methyl heptene-2; 6-methyl heptene-3; 3-ethyl hexene-l; 4-methyl-3-ethyl pentene-Z; 4,5-dimethyl heptene-Z; and 4,5,5-trimethyl hexene-2.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. The method of preparing butadiene which comprises forming a mixture of (a) at least one olefin from the group consisting of pentene-Z, hexene-2; 3-methyl pentene-1; and 3-methyl butene-l and (b) a cracking promoter comprising a mixture of (1) at least one material from the group of benzene, toluene, and Xylene and (2) hydrogen sulfide, the materials of each of group (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (1) to the material in (2) ranging from about l/ 1 to about 20/1, subjecting Said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about p.s.i., to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming butadiene and recovering said butadiene.

2. The method of preparing isoprene which comprises forming a mixture of (a) at least one olefin from the group of Z-methyl pentene-2; 3-methyl pentene-2; 2-ethyl butene-l; 3,3-dimethyl butene-l; 2,3-dimethyl butene-l; 2-methyl hexene-Z; 3-methyl hexene-Z; 2-ethyl pentene-l; 2,3-dimethyl pentene-l; and 3,3-dimethyl pentene-l and (b) a cracking promoter comprising a mixture of (1) at least one material from the group of benzene, toluene, and xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (1) to the material in (2) ranging from about 1/1 to about 20/1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about 100 p.s.i., to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming isoprene and recovering said isoprene.

3. The method of preparing 2-ethyl butadiene-1,3 which comprises forming a mixture of (a) at least one olefin from the group consisting of 3-ethyl pentene-Z; 2- ethyl pentene-Z; and 3-ethy1 hexene-2 and (b) a cracking promoter comprising a mixture of (l) at least one material from the group of benzene, toluene, and xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (l) to the material in (2) ranging from about 1/1 to about 20/ 1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about 100 psi to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming 2-ethyl butadiene-1,3 and recovering said 2-ethyl butadiene-1,3.

4. The method of preparing 2,3-dimethy1 butadiene-1,3 which comprises forming a mixture of (a) at least one olefin selected from the group of 2,3-dimethyl pentene-Z; 3-methyl-2-ethyl butene-l; 2,3,3-trimethyl butene-l; 2-isopropyl pentene-l; 2,3,3-trimethyl pentene-l; and 2,3-dimethyl heptene-Z and (b) a cracking promoter comprising a mixture of (1) at least one material from the group of benzene, toluene, and Xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (1) to the material in (2) ranging from about 1/1 to about 20/1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about 100 p.s.i., to cleave the carbon-tocarbon single bond Which is in the position beta to the double bond of said olefin, thereby forming 2,3-dimethyl butadiene-l,3 and recovering said 2,3-dimethyl butadiene- 1,3.

5. The method of preparing 3-methyl pentadiene-l,3 which comprises forming a mixture of (a) at least one olefin from the group consisting of 3-methyl hexene-3; 3- methyl heptene-3; and 2,4-dimethyl hexene-2 and (b) a cracking promoter comprising a mixture of (l) at least one material from the group of benezene, toluene, and xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (1) to the material in (2) ranging from about 1/1 to about 20/1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about 100 p.s.i., to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming 3-methyl pentadiene-l,3 and recovering said S-methyl pentadiene-l,3.

6. The method of preparing Z-methyl pentadiene-l,3 and 4-methyl pentadiene-l,3 which comprises forming a mixture of (a) at least one olefin from the group consisting of 2,4-dimethyl pentene-Z; Z-methyl heptene-3; 4,4-dimethyl hexene-Z; and 2-propyl pentene-Z and (b) a cracking promoter comprising a mixture of (l) at least one material from the group of benzene, toluene, and xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (1) to the material in (2) ranging from about 1/1 to about 20/ 1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about p.s.i., to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming Z-methyl pentadienel,3 and 4-methyl pentadiene-l,3 and recovering said Z-methyl pentadiene- 1,3 and 4-methyl pentadiene-l,3.

7. The method of preparing piperylene which comprises forming a mixture of (a) at least one olefin from the group consisting of hexene-3; 4-methyl pentene-2; hep-l tene-3; 4-methyl hexene-2; 4-methyl heptene-2; G-methyl heptene-3; and 3-ethyl hexene-l and (b) a cracking promoter comprising a mixture of (l) at least one material from the group of benezene, toluene, and xylene and (2) hydrogen sulfide, the materials of each of groups (1) and (2) being present in said mixture in an amount of at least one mol percent based on the olefin, said ratio of the materials in (l) to the material in (2) ranging from about 1/ 1 to about 20/1, subjecting said mixture to temperatures ranging from about 400 C. to about 900 C. for periods of time varying from about 0.05 to about 0.5 second and at pressures not greater than about 100 p.s.i., to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin, thereby forming piperylene and recovering said piperylene.

8. The method according to claim 2 in which 3-methyl pentene-2 is subjected to temperatures ranging from about 600 C. to about 750 C. While in the presence of steam at a mol ratio of Water to hydrocarbon of approximately 3/ 1 and a mixture of about 5 to about 10 mol percent of hydrogen sulfide and from about 5 to about 10 mol percent of toluene based on the mols of said 3-methyl pentene-2.

9. The method according to claim 2 in which 2-methyl pentene-Z is subjected to temperatures ranging from about 600 C. to about 750 C. While in the presence of steam at a mol ratio of Water to hydrocarbon of approximately 3/1 and a mixture of about 5 to about 10 mol percent of hydrogen sulfide and from about 5 to about 10 mol percent of toluene based on the mols of said 2-methyl pentene-Z.

FOREIGN PATENTS 605,357 l0/1961 Belgium.

PAUL M. COUGHLAN, JR., Primary Examiner. 

1. THE METHOD OF PREPARING BUTADIENE WHICH COMPRISES FORMING A MIXTURE OF (A) AT LEAST ON OLEFIN FROM THE GROUP CONSISTING OF PENTENE-2, HEXENE-2; 3-METHYL PENTENE-1; AND 3-METHYL BUTENE-1 AND (B) A CRACKING PROMOTOR COMPRISING A MIXTURE OF (1) AT LEAST ON MATERIAL FROM THE GROUP OF BENZENE, TOLUENE, AND XYLENE AND (2) HYDROGEN SULFIDE, THE MATERIALS OF EACH OF GROUP (1) AND (2) BEING PRESENT IN SAID MIXTURE IN AN AMOUNT OF AT LEAST ONE MOL PERCENT BASED ON THE OLEFIN, SAID RATIO OF THE MATERIALS IN (1) TO THE MATERIALS IN (2) RANGING FROM ABOUT 1/1 TO ABOUT 20/1, SUBJECTING SAID MIXTURE TO TEMPERATURES RANGING FROM ABOUT 400*C. TO ABOUT 900*C. FOR PERIODS OF TIME VARYING FROM ABOUT :.05 TO ABOUT 0.5 SECOND AND AT PRESSURES NOT GREATER THAN ABOUT 100 P,S.I., TO CLEAVE THE CARBON-TO-CARBON SINGLE BOND WHICH IS IN THE POSITION BETA TO THE DOUBLE BOND OF SAID OLEFIN, THEREBY FORMING BUTADIENE AND RECOVERING SAID BUTADEIENE. 